Flat-panel displays have recently been utilized in various products and fields. These flat-panel displays have been desired to have a larger size, higher display qualities, and lower power consumption.
Organic electroluminescent display devices including organic EL elements that utilize electroluminescence (hereinafter, also abbreviated as “EL”) of an organic material have drawn much attention as an all-solid-state flat-panel display with excellent properties of low voltage driving, high-speed response, and a self-luminous property.
An organic EL display device includes thin-film transistors (TFTs) and organic EL elements connected to the TFTs on a substrate such as a glass substrate.
The organic EL elements are light-emitting elements capable of providing a high-luminance light when driven by low-voltage direct current, and each have a structure in which the first electrode, an organic EL layer, and the second electrode are laminated in the stated order. The first electrodes are connected to the TFTs. The organic EL layers each have a structure in which organic layers such as a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer are laminated.
A full-color organic EL display device typically includes organic EL elements in three colors of red (R), green (G), and blue (B), as the sub-pixels. The sub-pixels are aligned in a matrix on a substrate, and sub-pixels in these three colors constitute each pixel. The display device provides images by selectively allowing the organic EL elements to emit light with the desired luminance values, using the TFTs.
In production of such an organic EL display device, patterned light-emitting layers corresponding to sub-pixels are formed from organic light-emitting materials.
One method for forming the light-emitting layer by patterning having been developed recently utilizes a mask smaller than the substrate to carry out vapor deposition on the entire substrate while moving the substrate relative to the mask and the vapor deposition source, so that organic EL elements are formed on the substrate that is larger than the mask (e.g. Patent Literatures 1 to 5). Hereinafter, such a method for carrying out vapor deposition while moving (scanning) the substrate relative to the mask and the vapor deposition source is also referred to as scanning vapor deposition.